Novel multifunctional azo initiators for free radical polymerizations: methods of preparation

ABSTRACT

The invention provides compositions of matter, methods of their synthesis, and methods of their use in polymerization reactions. The compositions include polyfunctional initiators used to make star polymers when polymerized with monomers. The polyfunctional initiators are synthesized out of a multifunctional core with at least two functional groups and two or more initiator units bonded to the functional groups. The initiator units have two electron-withdrawing groups bonded to a central carbon atom and an azo group between the central carbon atom and the functional group. The polyfunctional initiators are particularly effective because when they decompose to form the radical core of a star polymer, the electron-withdrawing groups prevent the corresponding radical from forming any linear polymer contamination and only desired star polymers result.

CROSS-REFERENCE TO RELATED APPLICATIONS

None.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

BACKGROUND OF THE INVENTION

The present invention relates to synthesis of thermolabilemultifunctional azo compounds and their use for the preparation of highmolecular weight well-defined structured polymers. As described forexample in U.S. Pat. Nos. 6,605,674, 6,627,719, and 6,753,388 these azocompounds are particularly useful for the synthesis of flocculants,coagulants and dispersants for paper, mining and wastewater industries.

Well-defined macromolecular architectures are typically prepared byliving anionic or cationic polymerization or by controlled radicalpolymerizations such as RAFT (Reversible addition-fragmentation chaintransfer), ATRP (Atom Transfer Radical Polymerization), NMP(Nitroxide-Mediated Polymerization) and more recently SET-LRP (SingleElectron Transfer-Living Radical Polymerization). Each of these methodshave limitations, such as monomer compatibility, purity of reactants,reaction medium, heavy metal contamination in the final product, longerreaction times, and an inability to achieve high molecular weights. Froman industrial point of view these polymerizations are not enticing dueto the processing cost and selectivity towards monomers and reactionconditions. Traditional free radical polymerization is widely usedindustrially for polymer synthesis, due to the ease of synthesis and theability to avoid the limitations of the prior methods. However, theability to control the concise architecture of the final product usingtraditional free radical methods is limited.

There are many ways to manipulate the architecture of macromolecules.Star polymers gained much attention in the last two decades and therehave been numerous publications on its synthesis and properties of theresulting polymers. The two most common ways to make star polymers are(1) start with a multifunctional initiator (as shown in FIG. 1) and (2)covalently attach a preformed polymer to a polyfunctional core.Polyfunctional initiators result in polymers of high molecular weightsand in the synthesis of very large macromolecules (MW several millions)the first route is the preferred method of preparation.

Synthesis of linear macromolecules from azo initiators are widely knownand have been practiced for many years. AIBN (Azobisisobutyronitrile) isone of the most commonly used initiator molecule in the industry andacademia due to its cost, availability, solubility and decompositiontemperature. Upon decomposition a molecule such as AIBN generates amolecule of N₂ and two equally reactive radicals capable of initiatingpolymerization, which could lead to two linear polymers. There arenumerous publications available on the manipulation of azo groups togain better control on the final architecture of the macromolecule.Several detailed reviews on azoderivatives are available in theliterature; especially reviews by C. I. Simionescu et al. covers most ofthe work done in this area. (Prog. Polym. Sci., 1986, 12, 1-109;Romanian chemical quarterly reviews 1995; 3(2), 83-103).

There are very few useful multifunctional initiators capable ofinitiating polymerization. The main drawback with multifunctionalinitiators is that upon decomposition, a second radical produces linearpolymers in addition to the desired star polymers. For example, (asillustrated in FIG. 3) a prior art composition commercially known asArkema's Luperox JWEB50 is a multifunctional (four functional) organicperoxide, which upon decomposition yields a tetra functional initiatorand four tertbutoxy radicals which each could produce linear polymers.(Penlidis et al,: Poly Bull 2006, 57, 157-167 and Penlidis et al:Macromol Chem Phys 2003, 204, 436-442). In order to exclusively makestructured polymer these tertbutoxy radicals need to be prevented frominitiating polymerization reactions.

U.S. Pat. No. 4,929,721 teaches the preparation of azo side groups onthe polymer backbone by copolymerization. The azo groups on theresulting polymer may be used for post modification of the polymer. Theazo groups reported by this patent have two main problems; first, thedecomposition temperature of this molecule is too high to be practicallyused as a polymerization initiator for inverse emulsion polymerization.Their objective was to keep this molecule stable during polymerizationand activate only for post modification. This patent reports theircompounds to be very stable at 130° C. The second problem with thisapproach is that this will also create the linear polymers in additionto graft copolymers.

International Patent Application WO/0224773 teaches the synthesis ofbranched polymers. In this teaching they have taken into account of thefact there could be linear polymers formed. This was eliminated bymaking sure the second radical is unable to initiate the polymerization.However, this teaching also fails to make well-defined cores to makewell-defined star polymers. Both of the above teachings makes use of thevinyl groups to homo or co-polymerize the azo groups onto a polymer andthe azo groups are activated at a later time for further modification ofthe polymer or at the same time to make highly random branches.Activation of the azo side groups at the same time as the backbonesynthesis will lead to highly branched but a poorly definedarchitecture. This approach in flocculent synthesis will result inhighly closed architecture, which are known to be very ineffective.

The art described in this section is not intended to constitute anadmission that any patent, publication or other information referred toherein is “prior art” with respect to this invention, unlessspecifically designated as such. In addition, this section should not beconstrued to mean that a search has been made or that no other pertinentinformation as defined in 37 C.F.R. §1.56(a) exists.

BRIEF SUMMARY OF THE INVENTION

At least one embodiment is directed towards a polyfunctional initiatorcomprising a multifunctional core bonded to at least two initiatorunits. Each initiator unit comprises two electron-withdrawing groupsbonded to a central carbon atom and an azo group between the centralcarbon atom and the multifunctional core.

At least one embodiment is directed to a polyfunctional initiator inwhich the multifunctional core comprises at least two end atoms. Eachend atom is bonded to an initiator unit. The atom of each end atom isselected from the list consisting of oxygen, carbon, and nitrogen. Themultifunctional core spans at least one string with a string length ofbetween 2 and 100 atoms between each end atom not including the endatoms. The atoms within the string are selected from the list consistingof oxygen, carbon, and nitrogen.

At least one embodiment is directed to a polyfunctional initiator inwhich the multifunctional core further comprises between 1 and 4branching atoms. Each branching atom is an atom within at least threedifferent strings. Each branching atom is engaged at all of its bindingsites to other atoms within a string and is selected from the listconsisting of carbon and nitrogen.

One architecture of the polyfunctional initiator is according to FormulaI:

wherein:

-   R is a multifunctional core with at least two functional groups, R₁    is a linker group selected from the list consisting of: an amide    whose carbonyl group is attached to nitrogen and is attached to R₂    by the nitrogen; an ester whose carbonyl group is attached to oxygen    and is attached to the R₂ by the nitrogen; and an ether group in    which the oxygen is attached to R₂, R₂ is a hydrocarbon having    between 4 and 20 carbon atoms. At least one of R₃ and R₄ are an    electron-withdrawing group. One of R₃ and R₄ can be an electron    donating group. R₅ is hydrocarbon having between 1 and 50 carbon(s);    and X is greater than 1.

The multifunctional core R can be one selected from the list consistingof: 2, 2′, 2″-Nitrilotriethylamine, triethanol amine, pentaerythritoland its derivatives, dendritic molecules, multifunctional amines,multifunctional acid chlorides, multifunctional carbonyls,multifunctional esters, and multifunctional alcohols. R₁ can be selectedfrom the list consisting of: two or more alkyl groups, two or more arylgroups, and alkyl and an aryl group as well as a linear substitutedalkyl group, a non-linear substituted alkyl group, a linearunsubstituted alkyl group, a non-linear unsubstituted alkyl group, alinear substituted aryl group, a non-linear substituted aryl group, alinear unsubstituted aryl group, a non-linear unsubstituted aryl group,a linear substituted cyclo alkyl group, a non-linear substituted cycloalkyl group, a linear unsubstituted cyclo alkyl group, and a non-linearunsubstituted cyclo alkyl group.

In at least one embodiment, at least one of the electron withdrawinggroups are selected from the list consisting of CN, CONR₆R₇ and COOR₈wherein: R₆, R₇, and R₈ are each one selected from the list consistingof hydrogen, a linear alkyl group, a linear aryl group, a linear alkoxygroup, a linear amino group, a linear alkylamino group, a linearhydroxyl group, a branched alkyl group, a branched aryl group, abranched alkoxy group, a branched amino group, a branched alkylaminogroup, and a branched hydroxyl group. In addition, R₅ can be selectedfrom the list consisting of: a linear alkyl group, a non-linear alkylgroup, an aryl alkyl group, a non-linear aryl group, and any combinationthereof.

At least one embodiment is directed towards a method of synthesizing apolyfunctional initiator comprising the steps of: synthesizing two ormore initiator units; synthesizing one or more multifunctional coreseach having more than one functional group; and coupling each functionalgroup to an initiator unit. In at least one embodiment the initiatorunits comprise two electron-withdrawing groups bonded to a centralcarbon atom and an azo group between the central carbon atom and themultifunctional core. The step of synthesizing two or more initiatorunits further comprises the steps of: diazotization of an aryl amine;reacting the diazotized aryl amine with an alkyl malonitrile to form anaromatic diazo compound; and converting the carboxylic acid into an acidchloride. In at least one embodiment the aryl amine is formed fromreacting 3-Aminobenzoic acid with sodium nitrite to form a diazoniumion.

In some embodiments the alkyl malonitrile is isopropyl malonitrile. Insome embodiments the acid is converted into an acid chloride using PCl₅,the halide is chlorine and the synthesis further comprises the step of:replacing the bond connecting the halide atom to the acid with a bondconnecting the functional group to the acid, and the functional group isan alcohol, an amine, or a sulfur based group.

At least one embodiment is directed towards a method of synthesizing apolymer comprising the steps of: providing at least one polyfunctionalinitiator comprising a multifunctional core bonded to at least twoinitiator units wherein each initiator unit comprises twoelectron-withdrawing groups bonded to a central carbon atom and an azogroup between the central carbon atom and the multifunctional core,providing a plurality of monomers, and reacting the at least onepolyfunctional initiator and plurality of monomers in a radicalpolymerization reaction.

BRIEF DESCRIPTION OF THE DRAWINGS

A detailed description of the invention is hereafter described withspecific reference being made to the drawings in which:

FIG. 1 is an illustration of the synthesis of a star polymer.

FIG. 2 is an illustration of the decomposition of a star initiator.

FIG. 3 is an illustration of a PRIOR ART star initiator.

FIG. 4 is a graph illustrating star polymer performances.

FIG. 5 is a graph illustrating star polymer performances.

FIG. 6 is a graph illustrating star polymer performances.

FIG. 7 is a graph illustrating dual feed polymer performances.

FIG. 8 is an illustration of a PRIOR ART polymer feed apparatus.

FIG. 9 is an illustration of a dual dosage polymer feed apparatus.

DETAILED DESCRIPTION OF THE INVENTION

For purposes of this application the definition of these terms is asfollows:

“Architecture” means the sequential arrangement of constituent groups ofa polymer, which results in the degree to which a polymer is linear,branched, structured, starred, or any combination thereof.

“Branching Atom” means an atom within two or more strings that is bondedto more than two atoms counted in a string.

“Floc” means a mass formed in a fluid through precipitation oraggregation of suspended particles.

“Initiator” means a composition of matter that initiates a radicalpolymerization reaction upon thermal decomposition.

“Initiator Unit” means that portion of a polyfunctional initiator thatis bound to the multifunctional core and is capable of initiating aradical polymerization reaction upon thermal decomposition.

“Hindrance Group” means a group that sterically impairs the ability of amonomer to react with a radical.

“Multifunctional” means having two or more arms or arm supportingregions.

“3-Functional Initiator” means an initiator having 3 arms.

“4-Functional Initiator” means an initiator having 4 arms.

“5-Functional Initiator” means an initiator having 5 arms.

“6-Functional Initiator” means an initiator having 6 arms.

“N-Functional Initiator” means an initiator having a number of armsequal to the integer N.

“Multifunctional Core” means a structural portion of a polyfunctionalinitiator bound to or capable of binding to two or more initiators. Themultifunctional core comprises two or more functional groups and eachfunctional group can bind one initiator to the core.

“4-Functional Peroxide Initiator” means an initiator having 4 armsaccording to the structure illustrated in FIG. 3 where D represents oneor more atoms. Luperox Jweb50 by Arkema is an example of a 4-FunctionalPeroxide Initiator.

“Polyfunctional Initiator” means a composition of matter containing twoor more sites capable of initiating a radical polymerization reactionafter thermal decomposition, which then anchor a repeating polymerchain. A polyfunctional initiator comprises at least one multifunctionalcore and two or more initiator units. A polyfunctional initiator mayhave more than one kind of initiator unit.

“Stable Radical” means a composition of matter having a radical siteformed after thermal decomposition, which is substantially incapable ofinitiating a radical polymerization reaction due to the effects of oneor more stabilizing groups in the composition of matter.

“String” means the smallest set of consecutive interconnected atoms (notincluding hydrogen) between two points on a molecule or between twopoints on a portion of a molecule, and does not include brancheddeviations from that set. The “string” between end atom A and end atom Z(which does not include A and Z in the count) in the following moleculehas a length of 6:

Any atom within a string can be in more than one string, so branchingatom B is within 4 strings (AZ, AM, JZ and JM).

“String Length” means the number of atoms in a string.

“Second Structuring Agent” means a structuring agent other than aninitiator.

“Structuring Agent” means a composition of matter, which facilitates theinterconnection of linear polymers to form structured polymers.

“Structured Polymer” means a polymer comprising two or more linearchains with two or more cross linkages interconnecting the linearchains.

In the event that a description of a term stated elsewhere in thisapplication is inconsistent with a meaning (explicit or implicit) whichis commonly used, in a dictionary, or stated in a source incorporated byreference into this application, the application and the claim terms inparticular are understood to be construed according to the descriptionstated in this application, and not according to the common definition,dictionary definition, or the definition that was incorporated byreference.

Referring now to FIG. 1 there is shown a 4-Functional Initiator starinitiator (1) comprising a multifunctional core (2) bound to 4 initiatorunits (3). When polymerized with monomer units a repeating chain (4)becomes anchored at each initiator unit (3). A star polymer (5) resultsfrom the extension of a repeating chain (4) being bound to multipleinitiator units (3). Some examples of uses of star initiators are foundin the co-pending, commonly owned, simultaneously filed applicationtitled “Novel Multifunctional Azo Initiators for Free RadicalPolymerizations: Uses Thereof” having an attorney docket number of 8184.

Embodiments of the present invention relate to the synthesis of novelmultifunctional azo initiators and the polymerization of structuredpolymers and copolymers of high molecular weight from these initiators.Embodiments of the invention are directed towards structured polymersobtained from radical polymerizations using initiators according toformula I:

Wherein R is a multifunctional core such as,2,2′,2″-Nitrilotriethylamine, triethanol amine, pentaerythritol and itsderivatives, or dendritic molecules with multiple functional groups. Thenumber of arms of the resulting polymer depends on the number offunctional group present in the core. The most common core groups aremultifunctional amines, acid chlorides or alcohols.

R₁ is a linker group such as an amide, an ester, or an ether group. Inat least one embodiment R₁ is an amide group having one or more carbonatoms, the endmost carbon atom being part of a carbonyl group attachedto a nitrogen atom. R₁ is engaged by one of the one or more carbon atomsto R. R₁ is engaged to R₂ by the nitrogen atom. In at least oneembodiment, R₁ is positioned within the initiator according to thefollowing formula where R_(X) represents a carbon bearing group:

In at least one embodiment R₁ is an ester group having one or morecarbon atoms, the endmost carbon atom being part of a carbonyl groupsingle bonded to an oxygen atom. R₁ is engaged by one of the one or morecarbon atoms to R. R₁ is engaged to R₂ by the single bonded oxygen atom.In at least one embodiment, R₁ is positioned within the initiatoraccording to the following formula where R_(X) represents a carbonbearing group:

In at least one embodiment R₁ is an ether group having one or morecarbon atoms, the endmost carbon atom being attached to an oxygen atom.R₁ is engaged by one of the one or more carbon atoms to R. R₁ is engagedto R₂ by the oxygen atom. In at least one embodiment, R₁ is positionedwithin the initiator according to the following formula where R_(X)represents 1 or more carbon atoms:

—R—R_(X)—O—R₂—

R₂ represent linear and non-linear, substituted or non-substitutedalkyl, aryl or cyclo-alkyl having 4 to 20 C atoms. R₃ and R₄ can be sameor different. At least one of R₃ and R₄ are electron withdrawing groupsincluding but not limited to CN, CONR₆R₇ or COOR₈ wherein R₆, R₇, and R₈are individually similar or dissimilar, and represent hydrogen, or alinear or branched alkyl, aryl group, alkoxy, amino, alkylamino, orhydroxyl groups or similar groups. One of R₃ and R₄ can be an electrondepositing group. R₅ represents linear or structured alkyl or arylgroups having 1 to 50 carbons and X is greater than or equal to 2.

As illustrated in FIG. 2, when the initiator (3) is heated it canthermally decompose, releasing a N₂ molecule and two radical containingunits (7, 8). One of the units (8) contains functional groups (6)capable of stabilizing the radical-containing species, preventing itfrom initiating a polymerization reaction. The second radical containingunit (7) receives no such stabilization, and is capable of initiating apolymerization reaction in a monomer solution. As that unit (7)containing the active radical species is bound to a multifunctionalcore, polymerization is only initiated from units bound to themultifunctional core. As the multifunctional core contains two or moreinitiators, and upon thermal decomposition the only active radicalspecies that could be formed are bound to the multifunctional core, theresultant polymer will be a star polymer.

In at least one embodiment, one or more of the stabilizing groups (6)are electron-withdrawing groups, which reduce the reactivity of thestable radical (8). The electron withdrawing groups can be engaged to acentral atom. If the central atom is a carbon, there can be 1-3electron-withdrawing groups. In at least one embodiment, anelectron-withdrawing group is selected from the list consisting of CN,CONR₆R₇, COOR₈, COOH, NO₂, and CF₃. In at least one embodiment, theelectron-withdrawing group comprises an aryl group engaged to thecentral atom and one item selected from the same list engaged to thearyl group.

In at least one embodiment, one or more of the stabilizing groups (6)are large steric hindrance groups. A steric hindrance group is a bulkygroup that either covers the radical site of the stable radical, orsufficiently blocks monomer access to the radical site therebypreventing the radical from reacting with monomers to form linearpolymers. In at least one embodiment, the steric hindrance group can beselected from the list of: linear, branched, aromatic, aliphatic groups,and any combination thereof that include between 4 and 100 carbon atoms.The steric hindrance group can comprise carbon, silicon, oxygen, sulfur,and any combination thereof.

In at least one embodiment, the multifunctional core comprises at leastone string extending between two end atoms. Each end atom is bonded toan initiator unit. When the multifunctional core thermally decomposes,the initiator radical remains engaged to the end atom while the stableradical is detached. The string comprises atoms selected form the listconsisting of oxygen, nitrogen, carbon, sulfur, silicon, and anycombination thereof The string atoms may be in the form of siloxane,carbonyl, amine (primary, secondary, and tertiary) groups, and maythemselves be engaged to other groups as well. The string may span from2 to 100 atoms between each end atom not including the end atoms. In atleast one embodiment, the end atom is bonded to a nitrogen atom thatwill become part of the generated N₂ molecule when the initiatordecomposes.

In embodiments in which the multifunctional core comprises more than twoinitiator units, the string also comprises branching atoms. Thebranching atoms are bonded to three or more non-hydrogen atoms, and liealong more than one string. When there is more than one initiator, foreach initiator unit there is at least one string extending between endatoms. The branching atoms can be saturated or unsaturated. Themultifunctional core may comprise chains of atoms that are not stringsextending between initiator units. Multifunctional cores may have eachstring run through a single branching atom, or there may be branchingatoms which branch off from other branching atoms thereby havingbranching atoms through which not every string passes. Branching atomsmay comprise any atom capable of bonding three or more other atoms. Theend atoms may be nitrogen, oxygen, silicon, carbon, or any atom capableof bonding two other atoms.

The following examples are presented to describe embodiments andutilities of the invention and are not meant to limit the inventionunless otherwise stated in the claims.

EXAMPLES 1) Initiator Synthesis

In at least one embodiment, the initiator unit was synthesized fromvarious components. Initiators having 2, 3, 4, 5, 6, and any number ofinitiator units are contemplated by this invention. The number ofinitiator units on each initiator depends on the multifunctional corethat the initiator is formed with.

In one embodiment, the multifunctional azo initiator was formed using aconvergent synthetic route, in which the initiator unit was synthesized,and then coupled to a multifunctional core. 3-(Azoisopropyl-malonitrile)benzoic acid was formed in yields greater than 95% through thediazotization of an aryl amine. 3-Aminobenzoic acid was treated withsodium nitrite to form a diazonium ion, which was then reacted withisopropyl malonitrile in the presence of sodium acetate to form theunsymmetrical azo initiator. Isopropylmalonitrile was synthesized vialiterature methods. (Dunham, J. C.; Richardson, A. D.; Sammelson, R. E.,Synthesis 2006, (4), 680-686, Sammelson, R. E.; Allen, M. J. Synthesis2005, (4), 543-546).

In at least one embodiment, the multifunctional azo initiator is formedby first converting the acid into the acid chloride using PCl₅.3-(Azoisopropylmalonitrile)benzoyl chloride readily forms esters oramides when reacted with alcohols or amines under standard reactionconditions.

2) 3-(Azoisopropylmalonitrile)benzoic acid

Concentrated HCl (96.4g) was slowly added to a solution of 100.4 g of3-aminobenzoic acid (3-ABA) in 1.98 L of H₂O in a 5L reactor, fittedwith a mechanical stirrer and a thermometer, and stirred until the 3-ABAwas dissolved. The solution was cooled to 3° C. on an ice bath, and thena chilled solution of 50.5 g of NaNO₂ in 410 mL H₂O was added quickly.The temperature of the reaction mix rose to 7° C., and a whiteprecipitate began to form. After 15 minutes, a chilled solution of 87.0g of isopropylmalonitrile, 78.0 g of sodium acetate in 710 mL of EtOHand 600 mL of H₂O are added to the reaction mix. A slight temperaturerise (5-10° C.) was observed again. A thick yellow solid precipitatedfrom the solution within 5 minutes. After 45 minutes, the product wasfiltered off, washed with a small amount of chilled H₂O, and dried for72 hours under vacuum to give 183.1 g (98%) of3-((isopropylmalonitrile)diazo)-benzoic acid. The structure wasconfirmed by ¹³C NMR and ¹H NMR.

3) 3-(Azoisopropylmalonitrile)benzoyl chloride

43.5 g of PCl₅ was added to a cooled solution (4° C., ice bath) of 50 gof 3-((isopropylmalonitrile)diazo)benzoic acid in 600 mL of CH₂Cl₂. Thetemperature rose slightly to 10° C. The mix was allowed to stir for 2hours at 4° C., then another 2 hours at room temperature. The solutionwas concentrated 50%, and 300 mL of hexanes was added. The precipitatewas removed from the mix by filtration, and the solution wasconcentrated to dryness to give 51.16 g of a dark brown oil (95%) of theacid chloride, which was used without any other further purification.The structure was confirmed by ¹³C NMR and ¹H NMR.

4) 3-Arm Star Initiator

A cooled solution containing 1.34 g of NEt₃ and 0.59 g oftris(2-aminoethyl)amine in 30 mL of CH₂Cl₂ was added to a solution of3.30 g of 3-((isopropylmalonitrile)diazo)benzoyl chloride in 50 mL ofCH₂Cl₂ at 3° C. under an N₂ atmosphere. The mix was stirred for 3 hours,and then quenched with 60 mL of brine. The aqueous layer was separatedand washed twice with 30 mL of CH₂Cl₂. The combined organic layers wasdried with Na₂SO₄, filtered, and concentrated under vacuum to give 3.29g of a yellow solid. The structure was confirmed by ¹³C NMR and ¹H NMR.

5A) Inverse Emulsion Polymerization

Preparation of Acrylamide/Dimethylaminoethyl Acrylate Methyl chlorideQuaternary Salt (50/50) copolymers.

An aqueous monomer phase was made up dissolving 9.82 g Adipic acid(Sigma-Aldrich, St. Louis, Mo.) and 34.78 g DI water in 227.74 g of49.5% aqueous solution of Acrylamide (Nalco Company, Naperville, Ill.).The components were stirred until a homogenous solution was formed. Tothis solution added 0.1 g of EDTA followed by 384.084 gDimethylaminoethyl acrylate methylchloride (DMAEA-MCQ, SNF Riceboro,Ga.) and mixed well. An oil phase was prepared from 274.96 g ofhydrocarbon solvent (Exxon Chemical Company, Houston, Tex.), 14.1 gArlacel SOAC (Uniqema, New Castle, Del.) and 16.3 g Tween 85 (Uniqema,New Castle, Del.) at room temperature. Oil phase was added to a 1500 mLreactor set at 40° C. When oil phase addition was complete rate ofmixing was increased from 500 rpm to 1000 rpm and added the monomerphase slowly into the oil phase. The mixing was accomplished by a 10 mmrod with a Teflon paddle at the base and 6-blade turbine mounted3-inches from the bottom. The resulting emulsion was mixed for next 30minutes. At 30 minutes the multifunctional azo initiator was added andstarted to purge the reaction with nitrogen (about 1 L/min). Theinitiator molecule (0.40 to 0.012 ) was charged as a solution in DMF, oras powder into the emulsion or it was semi batched over 2-4 hrs.Polymerization was started at 40° C. and during the reaction thetemperature was increase to 70° C. At the end of the polymerization thereaction held at 70° C. for one hour and cooled to room temperature. Apolymer solution was made up by mixing 2.0 g of water-in-oil emulsionand 198 g water with 0.12 g of nonionic surfactant alcohol ethoxylate(Clariant Basel, Switzerland), in a 300 ml tall beaker for 30 minuteswith vigorous mixing. An RSV of 19.2 dl/g (1M NaNO₃, 450 ppm, 30° C.)was measured for the polymer.

5B) Inverse emulsion polymerization of Acrylamide/Dimethylaminoethylacrylate methyl chloride quaternary salt copolymers usingmultifunctional initiator and other structuring agents such as MBA orHEMA

An aqueous monomer phase was made up dissolving 9.82 g Adipic acid(Sigma-Aldrich, St. Louis, Mo.) and 34.78 g DI water in 227.74 g of49.5% aqueous solution of Acrylamide (Nalco Company, Naperville, Ill.).The components were stirred until a homogenous solution was formed. Tothis solution added 0.1 g of EDTA followed by 384.084 gDimethylaminoethyl acrylate methylchloride (DMAEA-MCQ, SNF Riceboro,Ga.), followed by 2-5 g of 2-hydroxyethyl acrylate and/or 0.1 to 10 g of1% methylene bisacrylamide and mixed well. An oil phase was preparedfrom 274.96 g of hydrocarbon solvent (Exxon Chemical Company, Houston,Tex.), 14.1 g Arlacel 80AC (Uniqema, New Castle, Del.) and 16.3 g Tween85 (Uniqema, New Castle, Del.) at room temperature. Oil phase was addedto a 1500 mL reactor set at 40° C. When oil phase addition was completerate of mixing was increased from 500 rpm to 1000 rpm and added themonomer phase slowly into the oil phase. The mixing was accomplished bya 10 mm rod with a Teflon paddle at the base and 6-blade turbine mounted3-inches from the bottom. The resulting emulsion was mixed for next 30minutes. At 30 minutes the multifunctional azo initiator was added andstarted to purge the reaction with nitrogen (about 1 L/min). Theinitiator molecule (0.40 to 0.012 g) was charged as a solution in DMF,or as powder into the emulsion or it was semi batched over 2-4 hrs.Polymerization was started at 40° C. and during the reaction thetemperature was increase to 70° C. At the end of the polymerization thereaction held at 70° C. for one hour and cooled to room temperature. Apolymer solution was made up by mixing 2.0 g of water-in-oil emulsionand 198 g water with 0.12 g of nonionic surfactant alcohol ethoxylate(Clariant Basel, Switzerland), in a 300 ml tall beaker for 30 minuteswith vigorous mixing. An RSV of 10.8 dl/g (1M NaNO₃, 450 ppm, 30° C.)was measured for the polymer. Reactions were also conducted withmethylene bisacrylamide (but at much lower concentrations compared to2-hydroxycthyl acrylate) to obtain similar results.

5C) Inverse emulsion polymerization of Acrylamidc/Dimethylaminoethylacrylate methyl chloride quaternary salt copolymers using 4 functionalperoxide initiator

An aqueous monomer phase was made up dissolving 9.82 g Adipic acid(Sigma-Aldrich, St. Louis, Mo.) and 34.78 g DI water in 227.74 g of49.5% aqueous solution of Acrylamide (Nalco Company, Naperville, Ill.).The components were stirred until a homogenous solution was formed. Tothis solution added 0.1 g of EDTA followed by 384.084 Dimethylaminoethylacrylate methylchloride (DMAEA-MCQ, SNF Riceboro, Ga.) and mixed well.An oil phase was prepared from 274.96 g of hydrocarbon solvent (ExxonChemical Company, Houston, Tex.), 14.1 g Arlacel 80AC (Uniqema, NewCastle, Del.) and 16.3 g Tween 85 (Uniqema, New Castle, Del.) at roomtemperature. Oil phase was added to a 1500 mL reactor set at 50° C. Whenoil phase addition was complete rate of mixing was increased from 500rpm to 1000 rpm and added the monomer phase slowly into the oil phase.The mixing was accomplished by a 10 mm rod with a Teflon paddle at thebase and 6-blade turbine mounted 3-inches from the bottom. The resultingemulsion was mixed for next 30 minutes. At 30 minutes depending on thereaction 0.25 to 1.0 g of 4-functional peroxide (Arkema's Luperox®Jweb50) initiator was added and started to purge the reaction withnitrogen (about 1 L/min). Polymerization was started at 50° C. andduring the reaction the temperature was increase to 70° C. At the end ofthe polymerization the reaction held at 70° C. for one hour and cooledto room temperature. A polymer solution was made up by mixing 2.0 g ofwater-in-oil emulsion and 198 g water with 0.12 g of nonionic surfactantalcohol ethoxylate (Clariant Basel, Switzerland), in a 300 ml tallbeaker for 30 minutes with vigorous mixing. An RSV of 15.4 dl/g (1MNaNO₃, 450 ppm, 30° C.) was measured for the polymer.

Flocculation Performance of Copolymers

The effectiveness of various star polymers was demonstrated by a freedrainage test, which compared their flocculation and dewateringperformance. The polymer is activated by inverting it at a concentrationof typically 2200 mg/L on an actives basis in DI water under vigorousstirring using a cage stirrer at 800 rpm for 30 minutes. 200 mL ofsludge sample is conditioned with a specified volume of the polymersolution in a 500 mL cylinder by manually inverting the cylinder aspecified number of times, usually 5, 10 or 20 depending on the amountof shear to be simulated. Since the polymer dose is varied, a specifiedvolume of dilution water is added to the sludge prior to conditioning sothat the total volume of water added via the polymer and the dilutionwater is constant, usually 25 mL. The conditioned sludge is filteredunder gravity through a constant area of a belt press fabric, usuallyeither 41 cm² or 85 cm². The filtrate mass is measured as a function oftime via an electronic balance. The mass of the filtrate at a specifiedtime is plotted against polymer dosage for various polymers.

FIG. 4 illustrates the performance advantages of these new molecules at30 seconds of drainage in the dewatering of sludge from a chemicalindustry. An ideal polymer would show high drainage (high effectiveness)preferably occurring at low polymer dosage (high efficiency). A priorart linear polymer shows very low filtrate mass over a wide range ofpolymer dosage i.e. poor effectiveness. Increasing the polymer dosagefurther, reduces the drainage because of the so called “overdoseeffect”. In the “overdose effect” increasing the dosage of polymerbeyond its optimum value causes it to remain on the exterior of the flocaggregates which then adhere to the filtration fabric and blind it.Secondly, the excess polymer also increases the viscosity of thefiltrate, both of which contribute to a reduced drainage rate.

A prior art cross-linked polymer is effective (it drains higher amountsof water) but it is inefficient because it yields these results only athigh dosages. The cross-linked polymer also has a relatively level slopein the region of optimum dosage, indicating an absence of the overdoseeffect. 6-arm, 5-arm, 4-arm, and 3-arm polymers all show bettereffectiveness than the linear polymer and are more efficient than thecross-linked polymer because they function at lower dosages. The 3-armpolymer in particular matches the best effectiveness of the cross linkedpolymer, but at dosages less than that of the cross-linked polymer,indicating its superior efficiency.

FIG. 5 illustrates the effectiveness and efficiency of star polymersrelative to cross-linked and linear polymers at 10 seconds of drainagewhen applied to the dewatering of sludge from a refinery. It shows that3-arm, 4-arm polymers are nearly as effective at achieving high drainageand much more efficient in polymer dosage compared to the cross-linkedpolymer. The 3-arm, 4-arm and 5-arm star polymers are much moreeffective at achieving high drainage than the linear polymer. In atleast one embodiment, the star polymer is itself treated by crosslinking agents to form an even more structured star polymer having atleast one cross linkage between at least two star polymer arms inaddition to the multifunctional core. These even more structured starpolymers have enhanced dewatering properties.

FIG. 6 shows performance advantage of the polymers made using thesenovel initiators (labeled “Polyfunctional”) compared with prior artcross-linked, linear polymers, and peroxide initiator based polymers.The results show that the 3-arm, 4-arm star polymers made from the novelinitiators perform more effectively than the prior art linear polymerand the multifunctional peroxide initiator based polymer, and are moreefficient than the cross-linked polymer, with only marginal decrease ineffectiveness.

The superior performance of star polymers arises from their uniquesolution viscosity properties. The viscosity of a star polymer is highat a high solution concentration e.g. 0.5% wt product in water, butdecreases sharply at lower concentration e.g. below 0.3% wt product. Incontrast, the viscosity of a linear polymer is not as high as that ofthe star polymer at high concentration and decreases gradually withdecrease in solution concentration of the polymer. A cross-linkedpolymer shows a very low viscosity that is nearly independent ofconcentration in the concentration range of 0.5% wt to 0.05% wt. In theinitial stage of flocculation, the high viscosity star polymer solutionforms large floc aggregates of the primary particles in the sludgesuspension. Upon further mixing of the star polymer solution and thesludge suspension, the floc aggregates become more compact and densecompared to the case of a linear polymer solution, since its decreasingsolution viscosity allows faster rearrangement of polymer moleculeswithin the floe aggregate. This compact floe architecture releases morefree water, resulting in faster drainage, compared to the floes obtainedfrom conditioning with a linear polymer. A cross-linked polymer solutionwill also provide a compact floc architecture giving high drainagerates, but due to its low viscosity, will form small floes eachcontaining a smaller number of primary particles. Therefore, toflocculate all particles of a suspension, a larger polymer dosage of thecross-linked polymer is required, making it less efficient. A starpolymer combines the low dosage benefit of the linear polymer and thehigh drainage benefit of the cross-linked polymer, making it a superiorproduct.

In at least one embodiment the performance of one or more polymers canbe enhanced, by dosing the same quantity of polymer as a mixture ofsolutions with different polymer concentrations. The different polymerconcentrations have more than one viscosity. Dosing the polymer insolutions of two different viscosities increases drainage effectivenesscompared to dosing it as a solution of one concentration (and henceviscosity). The high viscosity solution forms large and compact floeaggregates as described above. At polymer dosages above the optimumvalue, the “overdose effect” described previously is mitigated by thelow viscosity solution, because it is easily incorporated into the floeaggregate, producing dense, non-sticky floes.

In at least one embodiment represented by FIG. 7, the performance of astar polymer is improved by this dual dosing process. The dual dosingprocess is even more effective with star polymers than with linearpolymers because the difference in viscosity with concentration is morepronounced in star polymers.

FIG. 7 specifically illustrates the results of an experimentdemonstrating the dual dosing process with a 4-arm star polymer on asludge sample from a refinery. In this experiment, a fixed quantity ofpolymer was fed as an equal combination of 0.5% wt solution and a 0.25%wt solution on a product basis. Both polymer solutions were injectedinto the sludge sample at the same time and mixed with the sludge forthe same number of inversions as the base case of 0.5% wt solutionalone. Thus, there was no confounding effect of different energies ofmixing or the improved drainage that is known to occur from a sequentialfeed of polymer. With increasing dosage, the proportion of the 0.25% wtsolution to the 0.5% wt solution increased, since the need was to avoidmore of the high viscosity solution (i.e. 0.5 % wt solution) atexcessive dosages. Replicates were run to check reproducibility.

As seen from FIG. 7, there is no decrease in drainage rate at excessivedosages when the dual concentration solutions are used, in contrast tothe decrease in drainage when the high polymer concentration solution isused. This is because any excess polymer is present as a low viscositysolution (in the dilute 0.25% wt form), which is much easier toincorporate into the interior of the floc, making it denser and lesssticky on the exterior surface. Thus, there is no fouling of thefiltration fabric at excessive dosage. This feeding scheme has theadvantage that the operating dosage window of the polymer is now largerand variations in the solids content of the influent sludge can be moreeasily handled.

Referring now to FIG. 8 there is shown a prior art feeder systemcommonly used in the industry for activating polymer into solution. Theprior art feeder adds neat polymer product (polymer as stored) and waterto a mixing chamber to a desired concentration and then outputs thepolymer solution at that concentration (Polymer Solution Output). Theprior art feeder includes a primary water input (Water 1) and asecondary water input (Water 2), which is an option for further dilutionof the polymer solution, as well as a Polymer Solution Output.

FIG. 9 illustrates a novel cost effective modification to the feedersystem, which allows for use of the dual dosing process with existingfeeder systems. In addition to a first water input (901) controlled by afirst valve (931) in fluidic communication with a mixing chamber (999)this feeder system has a second input pipe (912) extending the supply ofsecondary water input (902) to a second polymer solution output (922).This second input pipe (912) allows the contents of the first polymersolution output (921) to be further diluted into the second polymersolution output (922). The second input pipe (912) can be controlled bysecond valve (932).

The flow of water into the second polymer solution output (922) can becontrolled by a third valve (903) into a mixing pipe (955), while thefraction of first polymer solution output (921) to be diluted can becontrolled by a fourth valve (904) into a fourth pipe (914) which alsofeeds into the second polymer solution output (922). Using this methodand apparatus, a specified fraction of the first polymer solution output(921) can be diluted to a known concentration and fed into theapplication as the second polymer solution output (922), which is oflower viscosity. The first polymer solution output (921) and the secondpolymer solution output (922) can either be combined into a singlestream via a header just prior to the injection point into thesuspension to be flocculated, or can be fed as two different streams. Byregulating the third and fourth valves (903 and 904), any combination ofhigh viscosity and low viscosity polymer solutions can be injected intothe application for optimum drainage performance. In at least oneembodiment, the apparatus comprises a polymer input pipe (950)

While this invention may be embodied in many different forms, there areshown in the drawings and described in detail herein specific preferredembodiments of the invention. The present disclosure is anexemplification of the principles of the invention and is not intendedto limit the invention to the particular embodiments illustrated.Furthermore, the invention encompasses any and all possible combinationsof some or all of the various embodiments described herein. Any and allpatents, patent applications, scientific papers, and other referencescited in this application are hereby incorporated by reference in theirentirety.

The above disclosure is intended to be illustrative and not exhaustive.This description will suggest many variations and alternatives to one ofordinary skill in this art. All these alternatives and variations areintended to be included within the scope of the claims where the term“comprising” means “including, but not limited to”. Those familiar withthe art may recognize other equivalents to the specific embodimentsdescribed herein which equivalents are also intended to be encompassedby the claims.

This completes the description of the preferred and alternateembodiments of the invention. Those skilled in the art may recognizeother equivalents to the specific embodiment described herein whichequivalents are intended to be encompassed by the claims attachedhereto.

1. A polyfunctional initiator comprising a multifunctional core bondedto at least two initiator units wherein each initiator unit comprises atleast one radical stabilizing group bonded to a central atom and an azogroup between the central atom and the multifunctional core.
 2. Thepolyfunctional initiator of claim 1 wherein the at least one radicalstabilizing group is one selected from the list consisting of: anelectron-withdrawing group, a steric hindrance group, and anycombination thereof.
 3. The polyfunctional initiator of claim 1 whereinthe central atom is selected from the list consisting of: carbon,oxygen, and silicon.
 4. The polyfunctional initiator of claim 1 whereinthe multifunctional core comprises at least two end atoms; each end atomis bonded to an initiator unit, the atom of each end atom is selectedfrom the list consisting of carbon, oxygen, nitrogen, primary aminenitrogen, secondary amine nitrogen, tertiary amine nitrogen, sulfur,silicon, and siloxane silicon; the multifunctional core spans at leastone string with a string length of between 1 and 200 atoms between eachend atom not including the end atoms; the atoms within the stringcomprise at least one item selected from the list consisting ofsaturated carbon, unsaturated carbon, carbonyl carbon, saturatednitrogen, unsaturated nitrogen, and oxygen.
 5. The polyfunctionalinitiator of claim 3 further comprising between 1 and 4 branching atoms,each branching atom is an atom within at least three different strings,and is selected from the list consisting of carbon, nitrogen, andsilicon.
 6. The polyfunctional initiator of claim 1 according to formulaI:

wherein: R is a multifunctional core with at least two functionalgroups, R₁ is a linker group selected from the list consisting of: oneor more carbons, an amide, an ester, an amine, a silane, sulfur,silicon, a thiol, an ether, and any combination thereof R₂ is ahydrocarbon having between 4 and 100 carbon atoms having a structureselected from the list consisting of linear, branched, aromatic, andaliphatic, at least one of R₃ and R4 are radical stabilizing groups, R₅is hydrocarbon having between 1 and 50 carbon(s) or a radicalstabilizing group, and X is greater than
 1. 7. The polyfunctionalinitiator of claim 1 wherein the multifunctional core is one selectedfrom the list consisting of: 2,2′,2″-Nitrilotriethylamine, triethanolamine, pentaerythritol and its derivatives, dendritic molecules,multifunctional amines, multifunctional acid chlorides, multifunctionalesters, multifunctional acids, and multifunctional alcohols.
 8. Thepolyfunctional initiator of claim 6 wherein R₂ is selected from the listconsisting of a linear substituted alkyl group, a non-linear substitutedalkyl group, a linear unsubstituted alkyl group, a non-linearunsubstituted alkyl group, a linear substituted aryl group, a non-linearsubstituted aryl group, a linear unsubstituted aryl group, a non-linearunsubstituted aryl group, a linear substituted cyclo alkyl group, anon-linear substituted cyclo alkyl group, a linear unsubstituted cycloalkyl group, and a non-linear unsubstituted cyclo alkyl group.
 9. Thepolyfunctional initiator of claim 6 wherein R₅ is selected from the listconsisting of: a linear alkyl group, a non-linear alkyl group, an arylgroup, an electron withdrawing group, and any combination thereof. 10.The polyfunctional initiator of claim 5 wherein at least one of theelectron withdrawing groups are selected from the list consisting of CN,CONR₆R₇, COOR₈, COOH, NO₂, CF₃, and —C₆H₄,R₉ wherein: R₆, R₇, and R₈ areeach one selected from the list consisting of hydrogen, a linear alkylgroup, a linear aryl group, a linear alkoxy group, a linear amino group,a linear alkylamino group, a linear hydroxyl group, a branched alkylgroup, a branched aryl group, a branched alkoxy group, a branched aminogroup, a branched alkylamino group, and a branched hydroxyl group and R₉is selected from the group consisting of CN, CONR₆R₇, COOR₈, COOH, NO₂,and CF₃.
 11. The polyfunctional initiator of claim 1 constructed andarranged for use in a free radical polymerization reaction selected fromthe list consisting of: solution, suspension, bulk, emulsion, inverseemulsion, precipitation/dispersion, inverse suspension, and anycombination thereof.
 12. A method of synthesizing a star polymercomprising the steps of: providing at least one 4-functional peroxideinitiator having a multifunctional core and 4 initiator units, providinga plurality of monomers, decomposing at least two initiator units toform at least one initiator radical, and initiating a polymerizationreaction between each of the at least one initiator radicals and theplurality of monomers.
 13. The polyfunctional initiator of claim 12constructed and arranged for use in a free radical polymerizationreaction selected from the list consisting of: solution, suspension,bulk, emulsion, inverse emulsion, precipitation/dispersion, inversesuspension, and any combination thereof.